Protective sheets which can be applied to paint films of automobiles, which are in an incompletely cured state have been requested. A protective sheet generally comprises a polymeric sheet having formed thereon a pressure-sensitive adhesive layer and aims at the prevention of paint films of automobiles and the parts thereof from being damaged, frosted, discolored, etc., by various floating matters and colliding matters, such as dirts, dusts, acid rain, pebbles, etc., when loading automobiles, the parts thereof, etc., just finished painting on trucks, ships, trains, etc., and transporting them remote places such as overseas, etc. Such a protective sheet has the advantages to overcome difficult points in a conventional system of covering a paint film having a thickness of from 5 to 20 .mu.m comprising a wax paint, that uniform protection with a uniform paint film is difficult, the paint film may easily be stained, the paint film is weak in the protection function to colliding matters such as acid rain, pebbles, etc., a large labor is required for forming and removing the paint films, and also use of a solvent may cause environmental problems such as the waste liquid treatment, etc.
In the above system, when a two-pack urethane paint is used, paint films for automobiles in a completely cured state can be formed by a heat-curing treatment and an aging treatment after painting. However, the aging treatment can be practiced during the transporting time to overseas, etc. Therefore, a method of shortening the aging treatment time after the heat-curing treatment, adhering a protective sheet to the paint film of the automobile in an incompletely cured state, transporting the automobile, and utilizing the transporting time for a part of the aging time for completely curing the paint film, whereby the efficiency of the supply of the parts or the automobiles is improved has come into wide use.
However, in the conventional sheets for protecting paint films of automobiles, there is a problem that when the protective sheet is applied to a soft paint film or a incompletely cured paint film and is allowed to stand for a long period of time under an outdoor high temperature in summer, etc., the paint film is deformed at the edge portions of the pressure-sensitive adhesive layer, for example, edges of entrapped air or sheet edges, and the deformed traces are clearly observed.
When the thickness of the pressure-sensitive adhesive layer in the sheet for protecting paint films of automobiles is increased to protect the deformation of the paint film, a problem occurs that when the sheet is preserved in a roll state, the form of the roll is deformed by a telescope phenomenon, and in peeling the sheet from the paint film, adhesive remaining may occur at the edge portions of the pressure-sensitive adhesive layer.